Traction wheel drive



March 17, 1953 s TRANSEAU 2,631,460

TRACTION WHEEL DRIVE Filed Oct. 16, 1951 INVENTOR SHERMAN T. TRRNSEHATTORNEY Patented Mar. 17, 1953 UNITED STATES ATENT OFFICE- 2,631,460TRACTION WHEEL DRIVE Sherman T;Transeau, Riverside, N.-- J. ApplicationOctober 16, 1951, SeriaINo. 251,464

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The present invention relates to chain drives for bucket elevators andthe like and more particularly to an improved traction wheel therefor ofthe type shown and described in my copen'ding application, Serial No.194,584, filed November 8, 1950, of which this application is acontinuation-in-part.

In bucket elevators heretofore in use there have been two types of drivewheels generally used to transfer the torque of a driven shaft to theelevator chain, one of which is the common toothed sprocket drive wheeland the other the wellknown traction wheel having a smooth rim designedto fricti'onally engage the chain. Both have inherent disadvantages aswill be pointed out.

In the toothed sprocket wheel, a tooth on the wheel contacts the barrelor other part of the chain link on the up run and pulls the chain overand through the arc of the drive or head wheel, while releasing itscontact on the down run of the chain. This sprocket type wheel ispositive in its action in that any and all torque in the head shaft isdelivered to the elevator chain without any appreciable slippage betweenthe drive wheel and the chain. It is, however, subject to thedisadvantage that it creates excessive wear on parts and breakage. Thereis ever present a continuous Wear on both the tooth of the sprocketwheel and the elevator chain barrel or other parts due either toslippage of the chain barrel on the sprocket tooth, or to the rotationof the chain barrel against the sprocket tooth as the chain passesthrough the arc of the wheel. This wear and grinding action of the chainparts while in contact with the tooth of the sprocket Wheel is such thatit reduces the chain life to as little as ten per cent of the normallife of the chain.

The breakage referred to in the case of the sprocket wheel drive is dueto the fact that the sprocket wheel is a positive drive so that when theelevator becomes jammed by overloading or because of a foreign objectentering the elevator system, it is wrecked due to the breakage ofeither the chain or the tooth of the Wheel unless the torque is releasedthrough the use of suitable shear pin, slip coupling or other safetydevices. Furthermore, the cost of maintenance of the material-handlingequipment, and, consequently, the cost per ton of material handled ismaterially increased because as the chain joints wear, the originalpitch of the chain is increased and: as the barrels. of the chain wearthe sprocket wheel teeth, the pitch ofthe latter is also in!- creased.By reason of this pitch variation, not only in the chain but also in thesprocket wheel, the replacement of a worn chain makes itabsolutelynec'essary to also replace the sprocket wheel in order to havethem both of the same original pitch.

In the traction wheeltype of drive, the torque from the elevator driveshaft is transferred to the elevator chain through the friction of thechain coming in contact with the rim of the traction wheel.

Among the advantages of this traction wheel type is quietness ofoperation. Also, the lifeof the chain is at its maximum due to the factthat practically all of the grinding motion present in the tooths'procket'wheel' is eliminated. Furthermore, since the traction wheelhas a smooth surface, which is subject to little, if any, localizedwear, the pitch of the chain is not a factor, and, consequently, whenthe chain is replaced, it is unnecessary to replace the traction wheel.Another advantage is that only a given torque can be transferred fromthe elevatordrive shaft to the chain. When this torque is exceeded dueto a foreign object entering the elevator system, the chain slips onthe" traction wheel, making it impossible to wreak the elevator; Suchbeing the case, it is not necessary to incur the expense of installingshear pins, slip couplings or other such safety devices".

The disadvantages of the traction wheel drive are as follows: Due to thefact that only a fixed amount of torque" can be transferred from thetraction wheel to the chain, it is often impossible to drive theelevator chain by the conventional traction wheel. The factorsdetermining the amount of torque transferred from the traction Wheel tothe chai-n are the coefficient of friction between the two metals of thetraction wheel and the chain and. also the weight of. the material percubic foot being handled in the elevator system. Up to a given weight ofthe material being. handled by the chain elevator, the tractive pullwill be normally sufficient when it is 200% of the necessary pull tooperate the elevator. When, however, the tractive pull falls below thisnormal factor of 200%, the slippage between the chain and the tractionwheel will increase to the point where'the transfer'of' torque from thetraction wheel to the chain is insufficient to elevate the load;Therefore, for' satisfactory operation of the traction wheel drive, itis absolutely essential that a competent engineer have before him allpertinent data for efii cientinstallation and" operation of a chainelevator driven by the conventional traction wheel.

Having in mind the foregoing, it is among the principal objects of thepresent invention to provide an improved construction of traction wheelthe use of which obviates the disadvantages of both the toothed sprocketdrive wheel and the conventional traction drive wheel, while at the sametime retaining their advantages.

Another object of the invention is to provide a traction wheel in whicha safety factor is introduced in that the torque from the wheel to thechain can be increased or decreased according to conditions.

A still further object is to provide a traction wheel wherein any amountof torque can be delivered to a chain by the wheel without causingbreakage damage such as occurs through a positive drive.

Still another object is to provide a traction wheel having a combinedtorque-traction chainengaging rim which is made up of a plurality ofconvex projections or shoulders which are so spaced equally about thecircumference of the wheel rim as to present at least one projection orshoulder freely between each adjoining pair of the wheel-engagingbarrels of the chain and which are of such total number that thequotient obtained by dividing said total number by the number ofprojections or grooves per pitch of the chain is other than a wholenumber. By so designing the wheel, there is provided one extra so-calledhunting shoulder in its chain-engaging rim, which extra shoulder causesthe chain link barrels to shift forward to the extent of one shoulder orprojection upon each revolution of the wheel, thereby insuring evendistribution of wear over the full circumference of the wheel rim and somaterially prolonging the life of the wheel.

Other objects and advantages of the invention will appear more fullyhereinafter, it being understood that the present invention consistssubstantially in the combination, construction, location and relativearrangement of parts, all as described more fully hereinafter, as shownin the accompanying drawings and as finally pointed out in the appendedclaims.

In the accompanying drawings,

Figure 1 represents a side elevation of a traction wheel embodying apreferred form of the present invention and showing a portion of anelevator chain with the link barrels in section to illustrate thedriving relation of the wheel;

Figure 2 represents a section through the traction wheel per se with thechain omitted;

Figure 3 is a perspective view of a wheel constructed in accordance withthe principles of the present invention; and

Figure 4 is a perspective view showing the wheel operatively fitted witha bucket-type elevator chain of which latter only a portion is shown.

Referring now to the drawings, it will be observed that they show atraction wheel which, constructed in accordance with the principles ofthe present invention, comprises a hub if] having radially disposedspokes ll connected terminally with a circumferential rim 12 forconcentric turning movement. The hub It forms an internal bore l3 toreceive a driven shaft and has a keyway M to receive the usual key insuch a shaft for transmitting motion to the wheel.

.A threaded opening l5 traverses the hub in alinement with the keyway Hito receive a set 4 screw l6 (shown in Figure 2) to lock the wheel inplace upon the driven shaft.

The traction wheel of the invention is shown for use with a bucketelevator chain of the type formed by a plurality of chain links I!connected, one to another, by transverse pins l8 respectively formingpivotal bearings for cylindrical chain link barrels l9 transverselydisposed across the periphery of the rim 2 for traction driving by thewheel rim 52. Thus, the bucket elevator chain is in the form of anendless articulated unit made up of a plurality of chain links with thebarrels [9 of the several links spaced equally throughout the length ofthe elevator chain. While the drawing illustrates a bucket elevatorchain, it will be apparent and accordingly it is to be understood thatthe traction wheel of the present invention is applicable for use inconnection with any other type of endless chain made up of identicalarticulated links having uniformly spaced chain link barrels, such asthose designated by the reference numeral 19, as, for example, endlesschains employed for transmitting power from one shaft to another or foruse in connection with conveyors other than bucket elevators.

For the purpose of developing the required traction for driving theendless chain, the periphery of the rim [2 of the wheel is provided withan undulating or corrugated curvilinear surface formed by a plurality ofalternating open sided, transversely arranged concave grooves 28 andconvex projections or shoulders 2i, each of the grooves being formed onsuch a radius as to provide a traction surface generally complemental tothe periphery of the barrel l9 which rides therein. The projection 2 I,thus formed between each pair of adjacent grooves 20, is shaped as aconvex traction face of such radius as to cause it to merge smoothlyinto the continuing concave surfaces of the grooves 20. While the depthof the grooves 21? may be varied to increase or decrease the torque fromthe wheel to the chain, it is important that the depth should not besuch as to transform the convex projections into an abutmentcorresponding to the action of a tooth, a construction specificallyavoided by the present invention. To obtain the desired releasabletorque action, the depth of the grooves 20 should be less than theradius of the barrel entering such grooves, while the curvature of eachgroove should be of a radius preferably, but not necessarily, equal tothat of the chain link barrels. By the substantially uniform undulatingsurface the traction drive becomes a composite one of both torque andfriction, the wheel, however, being self-releasing from the torquecomponent when the elevator chain is subjected to overload or when itsfreedom of movement is impeded by a foreign object entering the elevatorsystem. In Figure 4, the modified traction wheel of the presentinvention is shown as associated with a single bucket type chain, uponwhich the materialhandling buckets 22 are mounted in any suitably spacedrelation.

It will be particularly noted that the projections or shoulders 21 areso spaced uniformly about the periphery of the wheel as to provide foran equal plural number of said projections or shoulders to be embracedby each of the chain links which are in engagement with the Wheel. Thus,as shown in Figure 1, four such projections or shoulders are providedper pitch of the chain, the chain pitch being, of course, the distancebetween the centers of successive barrels of the articulated chainlinks. Also, it will be noted that the total number of the projectionsor shoulders 2! spaced about the wheel periphery is such that thequotient obtained by dividing said total number by the number of saidprojections or shoulders per pitch of the chain is other than a wholenumber. Thus, in the wheel shown in Figure 1, four shoulders areprovided per pitch of the chain shown operatively associated with thewheel, with a total number of thirty-eight shoulders formed on thewheel, this total number being indivisible by the pitch number toprovide a whole number quotient.

Because of this relation between the total number of shoulders on thewheel and the number thereof per pitch of the associated chain, there isprovided at least One extra hunting shoulder in the wheel peripherywhich causes the chain link barrels to progressively advance about thewheel to the extent of one shoulder for each revolution of the wheel. Ofcourse, the total number of shoulders upon a given wheel may be variedas desired, but so long as said total number bears such relation to thepitch number as to provide other than a whole number quotient when theformer is divided by the latter, the desired extra shoulder is madeavailable to automatically efiect shifting of the chain barrelsprogressively into contact with all shoulders of the wheel upon rotationof the latter through a plurality of revolutions. Thus, uniform wear isinsured over the entire peripheral surface of the wheel with consequentprolongation of its service life.

The provision of a wheel having a plurality of projections or shoulders21 per pitch of the chain is of decided advantage in that it lessens theshock to which the wheel is subjected when the wheel and its associatedchain is operating under load. It will be apparent that the shock towhich the system is subjected depends partially upon the magnitude ofthe load and partially upon the distance through which the chain slipsrelatively to the wheel. The greater the extent of slippage, the greaterthe shock and the possibility of damage to and breakage of the Wheeland/or the chain. By providing a multiple number of shoulders withineach link of the chain, 1. e., per chain pitch, the permissible slippageof the chain operating under load is limited to but a fraction of thelength of the chain pitch, which slippage, in the instance illustratedin Figure 1 wherein the number of shoulders is four for the pitch of theassociated chain, is limited to a distance not exceeding one-third thelength of the chain pitch.

From the foregoing, it will now be apparent that a novel traction wheelhas been devised for driving endless chains for bucket elevatorconveyors and the like, wherein the disadvantages of prior drive wheels,such as the toothed sprocket and traction wheel types, have beeneliminated, while maintaining all the advantages thereof with addedefiiciency, safety, minimum repairs and minimum replacements.Furthermore, it will be evident that when the system is subjected to anoverload or other impediment to free movement of the endless chain, theconvex portions 2! of the traction wheel ride under the barrels of thechain links in engagement with the wheel and so permit the latter tofunction in the manner of a conventional smooth-surfaced traction wheelto relieve the system of all such torque as might seriously damage orcause breakage of the component elements of the system. On the otherhand, under conditions of normal load or even temporary overload, themodified traction wheel of the present invention provides such increasedtraction or coefficient of friction between the wheel and the elevatorchain as to materially increase the operating efficiency of the systemas a whole.

It will be understood, of course, that the present invention issusceptible of various changes and modifications which may be made fromtime to time Without departing from the general principles or realspirit thereof, and it is accordingly intended to claim the samebroadly, as well as specifically, as indicated by the appended claims.

What is claimed as new and useful is:

1. In combination with an endless chain of articulated links including aplurality of equally spaced transversely extending wheel engagingbarrels, a traction wheel comprising a hub and interconnected rim, saidrim having a combined torque-traction surface formed by a plurality ofcircumferentially spaced transversely extending concave grooves each ofwhich is smoothly merged with its next adjacent groove by a transverselyextending convex projection, said grooves being equally spaced and ofsuch total number that the quotient obtained by dividing said totalnumber by the number of grooves per pitch of said chain is other than awhole number.

2. In combination with an endless chain of articulated links including aplurality of equally spaced transversely extending wheel engagingbarrels, a traction wheel comprising a hub and interconnected rim, saidrim having a combined torque-traction surface formed by a plurality ofcircumferentially equally spaced transversely extending concave grooveseach of which is smoothly merged with its next adjacent groove by atransversely extending convex projection, the number of grooves perpitch of said chain being greater than one and the quotient obtained bydividing the total number of said grooves by the number thereof perpitch of said chain being other than a whole number.

3. In combination with an endless chain of articulated links each havinga transversely extending wheel engaging barrel, a traction wheelcomprising a hub and interconnected rim, said rim having a combinedtorque-traction surface formed by a plurality of circumferentiallyspaced transversely extending concave grooves each of which is smoothlymerged with its next adjacent groove by a transversely extending convexprojection, the number of grooves per pitch of said chain being greaterthan one and the quotient obtained by dividing the total number of saidgrooves by the number thereof per pitch of said chain being other than awhole number.

SHERMAN T. TRANSEAU.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 465,572 Diebold Dec. 22, 1891598,014 Schry Jan. 25, 1898 601,525 Pastor Mar. 29, 1898 647,243Anderson Apr. 10, 1900 1,008,330 Helms Nov. 14, 1911 2,572,601 De WildeOct. 23, 1951 FOREIGN PATENTS Number Country Date 412,879 France 1910

